U.S. Pat. No. 3,976,442 describes a process wherein a solid carbonaceous feed is transported in a CO2 rich gas to a burner of a pressurized gasification reactor operating at about 50 bar. According to the examples of this publication a flow of coal and carbon dioxide at a weight ratio of CO2 to coal of about 1.0 is supplied to the annular passage of the annular burner.
Process control is important in a process wherein solid carbonaceous feeds are partially oxidized. It has been found that the quality of the synthesis gas as obtained may vary, due to e.g. disturbances or variations in the solid carbonaceous stream and the oxygen containing stream being fed to the gasification reactor, the amount of ash in the carbonaceous stream, etc. If for example coal is used as the carbonaceous stream, variations in H2O content of the coal may result in altered process conditions in the gasification reactor, as a result of which the composition of the synthesis gas will also vary.
Various methods of controlling a partial oxidation process are known. For example GB-A-837074 describes a process wherein the carbon dioxide in the product gas of a partial oxidation process is measured to control the steam flow.
U.S. Pat. No. 2,941,877 describes a process for controlling the oxygen-to-carbon feed ratio in a partial oxidation reactor. The oxygen-to-carbon feed ratio is controlled by measuring the methane concentration in the product gas using infrared measurement technique. A disadvantage of using methane as the control input is that the signal is not a sharp signal, making control less accurate.
U.S. Pat. No. 4,851,013 describes a process wherein the partial oxidation process is performed in a pressurized gasification reactor provided with an inside wall consisting of conduits. The conduits are cooled by evaporation of water to steam inside the conduits. This results in a steam rate, which is measured and used as input to control the flow of either oxygen or solid carbonaceous feed, to said gasification reactor.
U.S. Pat. No. 4,801,440 describes a process for the simultaneous partial oxidation and desulphurization of a sulphur and silicate-containing solid carbonaceous fuel. In said process a slurry of solid feed and liquid carbon dioxide is fed to a partial oxidation reactor wherein partial oxidation and desulphurization takes place at a temperature of below 2000° F. (1093° C.). The amount of carbon dioxide is between 10 and 30 wt % basis on weight of feed.
It would be advantageous to provide a process to prepare a synthesis gas having less inert compounds, such as nitrogen, which process is effectively controlled.